Abstract: An activation-based injection device includes an activation unit (1, 2, 3), a vial unit (5) containing a drug and a needle (2) with an inner point (26) which never comes in contact with the external environment. The device is activated by a simple axial shift of the needle-shield (1) against the activation head (3). The latter is transparent and contains a window (45) of lower thickness. This allows the user to check the exact position of the needle hub (21) as a proof of tamper evidence, allowing the user to immediately determine whether the device has been previously activated or tampered with and if there is a risk that the drug has been contaminated.